1. Field of the Invention
The present invention relates generally to methods and apparatus for removing trihalomethanes and dissolved oxygen from water in order to render the water potable, and more particularly relates to methods and apparatus for continuously removing trihalomethanes and dissolved oxygen from water prior to using the water to make beverages.
2. Description of the Prior Art
In a typical water treatment system for potable water, the water is disinfected with chlorine. The organics present in water can react with chlorine to form trihalomethanes, among other products. The trihalomethanes (THMs) that are formed during chlorine disinfection of water are chloroform (CHCl3), bromodichloromethane (CHCl2Br), dibromochloromethane (CHClBr2) and bromoform (CHBr3). These trihalomethanes are known to be carcinogenic in nature. For the water to be potable, the concentration of trihalomethanes in the water must be very low. Currently, the maximum concentration of trihalomethanes in drinking water that is permitted by regulation is 100 .mu.g/lit (ppb), both in Canada and the United States (Environment Canada and U.S. Safe Drinking Water Act). However, it appears that in the near future this permissible concentration will be reduced further.
In the beverage industry, the concentration of trihalomethanes in the products is maintained at a level well below the value currently regulated by the federal laws. A typical action level for beverages is 80 ppb or lower. Currently the trihalomethanes from the beverage water are removed by adsorption on activated carbon. The activated carbon also removes residual chlorine. However, the lifetime of an activated carbon bed is much greater when it is used only in dechlorination, rather than both dechlorination and trihalomethane adsorption.
When activated carbon is used to remove trihalomethanes, the carbon bed becomes saturated with trihalomethanes quite quickly. The bed can be regenerated by steaming. Depending on the amount of trihalomethanes in the inlet water and the action level of trihalomethanes in the product water, the carbon bed can require frequent steaming. A large amount of steam is needed in each regeneration of the carbon bed. Further, after some definite number of times of regeneration, the whole carbon bed must be replaced by fresh carbon. On the other hand, if the carbon bed is used solely for the removal of merely chlorine, a carbon tower can typically last several years.
Apparatus for the continuous removal of volatile organic halogenated compounds from a liquid such as water are known, for example, from U.S. Pat. Nos. 4,892,664; 5,004,484; 5,470,478; 5,490,941; and Re. 35,074. A batch process for the removal of volatile organic halogenated compounds from a liquid such as water is known, for example, from U.S. Pat. No. 5,389,126, which could be made to be a continuous process. The disclosed apparatus generally addresses environmental concerns and none is disclosed to be employed in the purification of water for use in the preparation of beverages. Likewise, dissolved oxygen removal systems are known, for example, from U.S. Pat. Nos. 4,565,634; 5,383,958; and 5,766,321, however, no such apparatus is disclosed in combination with apparatus for removing volatile organic halogenated compounds from water.